Daniel deawbaugh



(No Model.)

D. DRAWBAUGH.

1 TELEPHONE TRANSMITTER.

1 No. 303,627. Patented Aug. 19,1884.

INVENTOR ESSES W i I 6 BY' ATTORNEY Nrrnfi) STATE s PATENT @FFICE.

DANIEL DRAVVBAUGH, OF EBERLYS MILL, PENNSYLVANIA, ASSIGNOR TO THEPEOPLES TELEPHONE COMPANY, OF NEW YORK.

TELEPHONE-TRANSM ITTER.

B?ECIFICATION forming part of Letters Patent No. 303,627, dated August19, 1884.

Applicatioufiled March 27, 1884. (No model.) 7

To aZZ whom it may concern:

Be it known that I, DANIEL DRAWBAUGH, of Eberlys Mill, Cumberlandcounty, Pennsyl- Vania, have invented a new and useful 1111- provementin Telephone Transmitters, of

which the following is a specification.

The invention relates to a telephone-transmitter containing threeelectrodes, two being rigidly attached to elastic bars or plates, towhich plates the diaphragm is secured, and the third and loose electroderesting upon the inclined faces of the fixed electrodes.

The invention consists in the construction more particularly hereinafterset forth.

Figural is a front view of the instrument with the outsideinclosing-case removed. Fig. 2 is a vertical section on the line as :vofFig. 1. Fig. 3 is a rear view of the diaphragm with the parts attachedthereto. Fig. 4 is the loose electrode, and Fig. 5 is the fixedelectrodes shown separately.

Similar letters of reference indicate like parts. t

A is the base or back board of the instrument. B B are two bars of woodattached thereto. 0 and D are two bars or strips of metal secured tothebar B by screws E, These bars are not in contact. Held in metal clipsE on the back of the bar 0 is an electrode, F, preferably of carbon.Held in similar clips, G, on the back of the bar D is a similarelectrode, H, of like material. The inner sides of these electrodes arebeveled or inclined, as shown in Fig. 5. I is an electrode of likematerial, of segmental form, having two plane faces, J and K. L is a rodinserted in the electrode I and loosely received in a conical socket, M,in the back board, A. The electrode I rests upon the beveled faces ofthe electrodes F and H, and forms a bridge between them, theseelectrodes F and H not being in contact. One of the plane faces of theelectrode I rests upon the beveled faces of the electrodes F H, and theother plane face lies just below the protruding clips E and G, but notin contact with said clips. The purpose of these clips is to prevent theelectrode I from becoming displaced when the instrument is moved about.To the front sides of the bars C and D are se- 50 cured two horizontalbars of ,wood, N and N,

and to these bars is secured the diaphragm O, whichIprefer to make alsoof wood. The diaphragm is perforated, as indicated at P, to allow ofaccess to the screws E. Q is an inclosing-case having a mouth-pieceopening, B. 5 5

Said case fits over the bars B,and is thus tightly held in place byfriction.

The circuits in the instrument 'proceed as follows: from the battery tothe binding-post lby awire, a, in the back of the case, to a post, b,thence to the primary of the induction-coil S, through said primary, andthence by a wire,

a, to a metal contact-plate, d, which is held between the upper screw Eand the bar B, and which is in contact with the metal bar G. The currentthen proceeds along the metal bar 0 to the electrode F, thence passes tothe loose or bridge electrode I, thence to the electrode H and bar D,thence to a post, 0, and thence by a wire, f, to the switch 9, and whenthe switch lever and point are in contact back to the battery. Thesecondary of the inductioncoil communicates by wires h h to posts i i,and these posts communicate by branch wires jj to the line binding-posts3 and 4:, and to binding- 7 5 posts 5 and 6, to which areceivingtelephone may be attached. I

It will be seen that by this construction the diaphragm is supportedsubstantially at its center and has free edges, and that the vibra- 8otions of the diaphragm are directly communicated to the elastic metalplates or bars 0 and D, which support the fixed electrodes. Thevibrations of the diaphragm due to the soundwaves produced by the voicecause variations 8 5 in the resistance offered by the electrodes to thepassage of the current. Said current is thereby modified so as to renderit undulatory and adapted for telephonic purposes. The electrodes arepreferably made of carbon. 0

I claim as my invention 1. The combination, in a telephone, of, adiaphragm attached substantially at its center to two elastic metallicsupports, not in" elec trical contact with each other, two electrodes 5inclined or having inclined faces secured upon said supports, and aloose electrode resting upon and bridging the fixed electrodes andsustained by said electrodes and a fixed support, substantially asdescribed.

elincd faces ,of said fixed electrodes, the said loose electrode beingprevented from sliding off the fixed electrodes by a projection fromsaid loose electrode entering and being loosely held in a socket in afixed support, substantially as described.

4. The combination of the back board, A, bars B, elastic metal bars 0I), attached to bars B, diaphragm O, a means of attaching said diaphragmsubstantially at its center to said bars, electrodes F and II, supportedupon bars 0 D, electrode I, anda projection thereon received in a recess0r socket on said back board, substantially as described.

5. In a telephone, the combination of the back board. A, bars B, anelastic support attached to said bars, a diaphragm secured substantiallyat its center to said support, and electrodes interposed between saidelasticsupport and a fixed support, substantially as de scribed.

6. In a telephone, the combination of the back board, A, bars B, anelastic support attached to said bars, a diaphragm secured substantiallyat its center to said support, eleetrodes interposed between saidelastic sup port and a fixed support, and the ease or cover Q,substantially as described.

DANIEL DRA\VBAUGH.

\Vitnesses:

PARK BENJAMIN, J. B. Cannon.

